The Animalcules, continued. 



129 



of the species are exceedingly abundant, occurring 

 in water where vegetable substances have decayed, 

 but rather to be expected when the active stage 

 of decay is over. Like the infusoria, they will 

 appear after a while in water where hay or leaves 

 have been infused a fact which Dr. Carpenter 

 connects with the circumstance that 

 these animalcules can be completely 

 dried, and will yet return to activity on 

 being moistened ; for he says they may 

 be wafted in a dry state in the atmos- 

 phere, and thus removed from place to 

 place. 



No. 18 represents the common wheel 

 animalcule (Rotifer vulgaris) which I 

 found repeatedly near the duckweed, as 

 well as among other water-plants. The 

 wheel-like organs show particularly well 

 in this specimen of the tribe. Their 

 appearance has been so often and so No 13 

 well described, that I need only vulgaris. A,giz- 

 remark that they do indeed look Sue v^siolt 

 exactly like a pair of pretty little 

 toothed wheels, revolving at a rapid rate. All this 

 is caused by the independent movement of the 

 separate cilia, as already explained, but the illusion 

 is so perfect, that we are not surprised to find that 

 the old microscopists thought these were really wheels; 

 thus the writer of the article " Animalcule," in the 

 Encyclopedia Britannica, edition of 1790, regularly 

 describes them as such, but informs us, whafc wo 



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